Even under aerobic conditions, cancer cells utilize primarily glycolytic metabolism to generate energy. It remains unclear if this shift from oxidative to glycolytic metabolism is required for cell growth and/or transformation, or occurs as a consequence of other cellular changes that are necessary for tumorigenesis. Expression profiling of transformed cells demonstrates that metabolic genes are among the most strongly upregulated groups of genes. Among the glycolytic enzymes with increased expression in cancer cells is the M2 isoform of the rate-limiting glycolytic enzyme, pyruvate kinase. In contrast to most adult tissues which express the M1 isoform, all cancer cells studied to date exclusively express the M2 isoform of pyruvate kinase (PK-M2). PK-M2 is necessary for establishing the unique metabolism of cancer cells. In addition, enzymatic activity of PK-M2 is regulated by tyrosine kinase-based growth signals. This proposed research will aim to establish the importance of PK-M2 for tumor formation and tumor maintenance in vivo. It will also define the importance of tyrosine kinase-based signaling in regulating PK-M2 activity, and identify how this regulation contributes to cancer biology. These studies will greatly advance our understanding of glycolytic regulation in cancer and will be important to determine how energy metabolism can be targeted to treat patients with cancer. RELEVANCE: A difference in cellular metabolism forms a key distinction between cancer and normal tissues that has not been exploited to treat human cancer. This study will test the consequences of altering metabolic regulation in cancer tissues, and will provide a model system to develop drugs targeting metabolic pathways that could change the way cancer is treated in patients.